What is the role of CSF lactate concentration in the workup of Haemophilus influenzae type b (Hib) meningitis?

Updated: Jul 09, 2018
  • Author: Prateek Lohia, MD, MHA; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Answer

In the setting of bacterial meningitis, CSF lactate is frequently elevated. Values in excess of 3.5-3.8 mmol/L are sensitive indicators of acute bacterial meningitis, found in as many as 92% of cases. The specificity of this finding is comparatively low, although elevation of lactate to the concentrations noted above is more strongly indicative of bacterial than viral meningitis. However, elevation of lactate does not exclude the diagnosis of viral meningitis.

Whether CSF lactate as a diagnostic test adds information that cannot be obtained from CSF cell counts, glucose, and protein is not clear. Moreover, elevated CSF lactate may be due to other potential alternative diagnoses (eg, closed head injury, smothering and other causes of hypoxic-ischemic brain injury, neoplasia, or prolonged seizures from any of a wide variety of causes).

Elevation of CSF lactate in Hib meningitis may be due to cerebral edema or changes in cell membranes or cellular energy metabolism leading to anaerobic glycolysis. CSF lactate may remain elevated for a fairly long time after effective antimicrobial therapy has resulted in amelioration of brain edema and restoration of ICP to the reference range.

Repeated lactate estimation (by lumbar CSF analysis or magnetic resonance imaging [MRI] spectroscopically) may provide a method for estimating possible deleterious effects of fluid restriction in cases of Hib meningitis–induced brain swelling. Inadequate systemic volume may be deleterious in such cases because of the high ICP and pressure-passive nature of dysregulation of cerebral circulation in meningitis.


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